Enhanced biohydrogen and lipid coproduction in Chlorella protothecoides under nitrogen-limiting conditions in a closed system

Abstract

This study was developed to explore the feasibility of achieving enhanced hydrogen (H2) and lipid coproduction mediated by H2-producing microalgae Chlorella protothecoides. C. protothecoides was able to simultaneously produce both H2 and lipids, and this H2 and lipid coproduction was found to be inducible under conditions of nitrogen limitation in a closed system. Specifically, optimal H2 (151.1 mL L−1) and lipid (49.6% DW) coproduction was achieved under 5% N in a closed system. Relative to nitrogen-replete conditions, such nitrogen limitation was able to induce the accumulation of NADPH and reactive oxygen species, thereby directly promoting lipid production. Moreover, in a closed system, these limited nitrogen levels established conditions of anaerobiosis, activating hydrogenase and thereby generating H2 while suppressing respiratory electron transport, ultimately further augmenting lipid production. Together, these results highlight a novel approach to simultaneously producing H2 and lipids and to enhancing such coproduction activity.